Cans = headphones, just another word that is sometimes used
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I've heard the LCD-2's with Fazor, but not many amps or DACs. I've heard the Benchmark DAC1 HDR, and the NFB-28, but no other amps or DACs.
Not sure what you're asking here, sorry. I think maybe you're asking about the O2/ODAC combo? If so, the O2/ODAC combo (amp and DAC) is a very cheap and clear sounding combo that is hard to beat for the price. The NFB-28 is also very clear, but you pay a lot more money for all the additional features. The sound is probably very similar - just a guess.
I currently use LCD-2's with Fazor and AKG Q701's with the NFB-28. It sounds great with both using the single ended output. I don't have the cables (XLR) to try balanced output yet.